WASHINGTON — NASA released this week five years of
data collected by the Wilkinson Microwave Anisotropy Probe
(WMAP) that refines our understanding of the universe and
its development. It is a treasure trove of information,
including at least three major findings:

New evidence that a sea of cosmic neutrinos permeates
the universe

Clear evidence the first stars took more than a
half-billion years to create a cosmic fog

Tight new constraints on the burst of expansion in the
universe's first trillionth of a second

"We are living in an extraordinary time," said Gary Hinshaw
of NASA's Goddard Space Flight Center in Greenbelt, Md.
"Ours is the first generation in human history to make such
detailed and far-reaching measurements of our universe."

WMAP measures a remnant of the early universe — its
oldest light. The conditions of the early times are
imprinted on this light. It is the result of what happened
earlier, and a backlight for the later development of the
universe. This light lost energy as the universe expanded
over 13.7 billion years, so WMAP now sees the light as
microwaves. By making accurate measurements of microwave
patterns, WMAP has answered many longstanding questions
about the universe's age, composition and development.

The universe is awash in a sea of cosmic neutrinos. These
almost weightless sub-atomic particles zip around at nearly
the speed of light. Millions of cosmic neutrinos pass
through you every second.

Relative constituents of the universe today,
and for when
the universe was 380,000 years old, 13.7 billion years ago.
Neutrinos
used to be a larger fraction of the energy of the universe
than they are
now.
Illustration courtesy WMAP Science Team

"A block of lead the size of our entire solar system
wouldn't even come close to stopping a cosmic neutrino,”
said science team member Eiichiro Komatsu of the University
of Texas at Austin.

WMAP has found evidence for this so-called "cosmic neutrino
background" from the early universe. Neutrinos made up a
much larger part of the early universe than they do
today.

Microwave light seen by WMAP from when the universe was
only 380,000 years old, shows that, at the time, neutrinos
made up 10% of the universe, atoms 12%, dark matter 63%,
photons 15%, and dark energy was negligible. In contrast,
estimates from WMAP data show the current universe consists
of 4.6% percent atoms, 23% dark matter, 72% dark energy and
less than 1 percent neutrinos.

Cosmic neutrinos existed in such huge numbers they affected
the universe's early development. That, in turn, influenced
the microwaves that WMAP observes. WMAP data suggest, with
greater than 99.5% confidence, the existence of the cosmic
neutrino background — the first time this evidence
has been gleaned from the cosmic microwaves.

Much of what WMAP reveals about the universe is because of
the patterns in its sky maps. The patterns arise from sound
waves in the early universe. As with the sound from a
plucked guitar string, there is a primary note and a series
of harmonics, or overtones. The third overtone, now
clearly captured by WMAP, helps to provide the evidence for
the neutrinos.

The hot and dense young universe was a nuclear reactor that
produced helium. Theories based on the amount of helium
seen today predict a sea of neutrinos should have been
present when helium was made. The new WMAP data agree with
that prediction, along with precise measurements of
neutrino properties made by Earth-bound particle
colliders.

WMAP cosmic microwave fluctuations over the full sky with
5-years of data. Colors represent the tiny temperature
fluctuations of
the remnant glow from the infant universe: red regions are
warmer and
blue are cooler.
Illustration courtesy WMAP Science Team

Another breakthrough derived from WMAP data is clear
evidence the first stars took more than a half-billion
years to create a cosmic fog. The data provide crucial new
insights into the end of the "dark ages," when the first
generation of stars began to shine. The glow from these
stars created a thin fog of electrons in the surrounding
gas that scatters microwaves, in much the same way fog
scatters the beams from a car's headlights.

"We now have evidence that the creation of this fog was a
drawn-out process, starting when the universe was about 400
million years old and lasting for half a billion years,"
said WMAP team member Joanna Dunkley of the University of
Oxford in the U.K. and Princeton University in Princeton,
N.J. "These measurements are currently possible only with
WMAP."

TEMPERATURE FLUCTUATIONS BY ANGULAR SIZE: The
first peak reveals a
specific spot size for early universe sound waves, just as
the length of
guitar string gives a specific note. The second and third
peaks are the
harmonics.
Illustration courtesy WMAP Science Team

A third major finding arising from the new WMAP data places
tight constraints on the astonishing burst of growth in the
first trillionth of a second of the universe, called
“inflation”, when ripples in the very fabric of space may
have been created. Some versions of the inflation theory
now are eliminated. Others have picked up new support.

Charles Bennett
Photo by Will Kirk / HIPS

"The new WMAP data rule out many mainstream ideas that seek
to describe the growth burst in the early universe," said
WMAP principal investigator, Charles
Bennett, of The Johns Hopkins University in Baltimore,
Md. "It is astonishing that bold predictions of events in
the first moments of the universe now can be confronted
with solid measurements."

The five-year WMAP data were released this week, and
results were issued in a set of seven scientific papers
submitted to the Astrophysical Journal. For further
information, see
wmap.gsfc.nasa.gov.

Prior to the release of the new five-year data, WMAP
already had made a pair of landmark finds. In 2003, the
probe's determination that there is a large percentage of
dark energy in the universe erased remaining doubts about
dark energy's very existence. That same year, WMAP also
pinpointed the 13.7 billion year age of the universe.

Additional WMAP science team institutions are: the Canadian
Institute for Theoretical Astrophysics, Columbia
University, University of British Columbia, ADNET Systems,
University of Chicago, Brown University, and UCLA.

Johns Hopkins University news releases can be found on the
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